The document discusses energy flow through ecosystems. It explains that: 1) Solar energy is absorbed by plants and used to produce food through photosynthesis. 2) Animals obtain energy by eating plants or other animals. As they are more active, there are typically more plants than animals. 3) When organisms die, decomposers like bacteria break down their bodies and recycle the energy and nutrients.

1. Energy Flow and Nutrient Cycles
Food Chains, Food Webs and
Ecological Pyramids

2. Energy Flow
What is our main source of
energy?

3. Energy Flow
• Solar/radiant energy from the sun is absorbed
by the chlorophyll pigments in green plants.
• This absorbed energy is then used by the
plants to produce food via photosynthesis.

4. Energy Flow
• Animals feed on plants either directly or
indirectly in order to obtain food and energy.
• Animals, like plants, use this energy for
growth, production of organic compounds,
and activities.

5. Energy Flow
• Animals are a lot more active than plants and,
as a result, require more energy than plants.
• Because of this, there are MANY more plants
than there are animals.

6. Energy Flow
It is evident then,
that energy is passed from
the sun, to plants to the
different levels of animals.

7. Energy Flow
What are the different levels of animals?
Hint: Think about their diets.

8. Energy Flow
• When plants an animals die, the decomposers
(what are these?) break up the dead bodies
and recycle the energy back into nature.
This is known as
ENERGY FLOW.

9. Energy Flow and Food Chains
• Energy Flow can be illustrated using food
chains, webs or pyramids.

10. Food Chains
• Food chains/webs/pyramids are illustrations
that demonstrate the path of energy as it
flows from one organism to another.
• The example below shows a simple food chain
in a grassland.
Green plant Rabbit Fox Bacteria

11. Activity
Complete the following activity individually
1. Make a list of some organisms that you have
seen in your garden at home or your
surroundings.
2. Draw a simple food chain to represent these
organisms and their feeding relationships.
3. Draw a simple food chain that could be
present in a fish tank.

12. Activity
Assess each other’s work and discuss some of
your answers

13. Food Webs
• The path taken by energy is much more
complicated than illustrated in a chain.
• Organisms obtain food from more than one
source or they may provide energy to more
than one type of organism.
• The resulting relationships look more like a
web than a chain.